A scanner is a device that is used to scan or read an image of a document, and are available as a standalone scanner or may be operationally incorporated into the image processing devices such as, for example, an electronic copier, facsimile or a multifunction apparatus that combines some of the functionalities of the afore-mentioned and other devices.
In order to read an images of a document, a scanner includes a scan sensor, i.e., an image sensor. When the focusing distance from the scan sensor to the document is fixed, the quality of the scanned image of the document may be compromised if the position of the document in relation to the scan sensor deviates from a predetermined range.
Moreover, the scanner may be required to perform at least an automatic type scanning, in which the scan sensor is stationary to scan a document being transported, e.g., by an automatic document feeder, past the scan sensor, and a manual type scanning, in which a document is manually placed on a platen and is scanned by the scan sensor moving across the document.
In some cases, the respective proper focus distance may not be the same for the automatic scanning and for the manual scanning for the possible reasons of the difference in the thickness of the platen and/or other design considerations. In order to scan a document at different focus distances to obtain a satisfactory scan quality using a single scan sensor, it may thus be desirable to be able to move the scan sensor in a focus direction, such as closer to or further from the document. It may also be desirable to accomplish such focusing movement of the scan sensor without significantly adding to the complexity and/or cost of the scanner.